PX4 Instability/Tuning Issue


I built a Tarot X4 quadrotor with Tmotor U7 2.0 420 KV motors and 18 inch props, powered by two 50C 6000mAh 6S batteries connected in parallel. The flight controller is cube orange.

The problem:

With Ardupilot the drone flies perfectly stable and tuned well easily.
With PX4 it is jittery, oscillatory, unstable straight off the ground and not tuning well either after spending days. Also the battery seems to drain unevenly going from 100% at take off to drastically low at around 40% shortly after take off while just hovering to tune manually.

Any suggestions what might be wrong, or are there any settings I am missing? I want to use PX4 but it seems to be not working at all. I have heard PX4 tuning process may be different from the Ardupilot due to different in algorithm type.

I really appreciate any help.


Can you upload a flight log, that will make it easier to help you? Otherwise it is quite hard to say exactly what your problem is


Yes below are few logs from cube orange testing the quadcopter (Tarot X4 kit built) while attempting to tune it:

Cube orange flight 1

Cube orange flight 2

Cube orange flight 3

In frustration with that cube orange, I ended up swapping it with a clean cube black in hopes that it may be hardware issue. I first tested it with an untuned arducopter and it worked flawless as it is. Then I deployed px4 on the same cube black and put it on a small quad (Tarot s500) and even without any tuning, it flew well. Then I finally put this cube black on Tarot X4 again which has been originally having the issues with instability, oscillation and crashes from cube orange. And the same thing happened again. Following is the log for first cube black px4 test on Tarot X4 kit setup.

Cube Black first flight without any tuning

This has taken months trying to figure out and not been making much sense. How it can fly so easily well with arducopter but not px4, while nothing else is different on it… and tuning also doesn’t seem to work. There was no way to auto-tune it, because quad is unstable or oscillatory always after a little while or right away, even on a calm day.

Your flight logs look quite weird. The only thing I can see from your logs is that it seems to have quite a bit of vibration. But since you can fly without any problems on ardupilot, that shouldn’t be the cause.
I would suggest going on PX4 discord and ask the question with the flight logs. On there you can find the developers who can help you with figuring out what goes wrong.

Thanks. I will add px4 discord channel. In the meanwhile, I tried to tune the drone and received the following results:

px4 cube black

I could see some improvements in roll and pitch, under altitude hold mode. The drone was oscillatory still under manual mode. I am afraid to try position hold still.

The drone was yawing sometimes or not very responsive on yaw. I wonder what could I do to make yaw tuned better. You can see in the PID analysis that there is no Step response for Yaw Rate appearing.